Wound healing is a complex physiological response to the injury. It is a very systemic biological, chemical, and mechanical event where the invaded pathogens removed from the damaged wound site for complete or partial remodeling of injured tissue. In general, it precedes in a very orderly and efficient manner characterized by three interrelated dynamic and overlapping phases, namely, inflammatory phase (consisting the establishment of homeostasis and inflammation; proliferative phase (consisting of granulation, contraction and epithelialisation) and finally the remodeling phase [1-3]. However, in severe pathologic conditions this cascade healing process is lost and the wounds are locked into a state of chronic inflammation characterized by abundant neutrophil infiltration with associated release of inflammatory mediators including reactive oxygen species, reactive nitrogen species and their derivatives. These radicals will result in oxidative stress leading to lipid peroxidation, DNA breakage, and enzyme inactivations ultimately cause local and distant pathophysiological inflammatory effects [1,4]. Mitigation of this dysregulated chronic inflammation (the major cause of impaired wound healing) and finding a safe and efficacious anti-inflammatory agent is a frontier challenge in modern medicine. However, the role of oxidants in the pathogenesis of many inflammatory diseases suggests that antioxidant has effective strategy for therapeutic approaches to such disorders [5]. To this end, anti oxidant activities of the traditional medicine give a new horizon for better healing treatment. Topical applications of compound with free radical scavenging properties have shown significant improvement in wound healing and protect tissue from oxidative damage [6]. In this regard, topical application of the upcoming anti-inflammatory drug modality of natural herbal extracts curcumin and its antioxidants properties will be certainly benefit against oxidative damage and be helpful to the better healing of the wound.
Curcumin (diferuloylmethane), a naturally occurring photochemical derived from the rhizome of turmeric (Curcuma longa). It has low intrinsic toxicity but a wide range of pharmacological activity including anti-oxidant, anti-inflammatory and anti-infective properties [7-10]. The antioxidant activity of curcumin could be attributed to the phenolic and the methoxy groups in conjunction with the 1,3-diketone conjugated diene system, for scavenging of the oxygen radicals. In this view, several in vitro and in vivo studies have demonstrated the effectiveness of curcumin to decrease the release of inflammatory cytokines like interleukin (IL)-8 and tumour necrosis factor (TNF-α) from monocytes and macrophages and further to inhibit enzymes associates with inflammation, such as cyclo-oxygenase (COX)-2 and lipoxygenase (LOX) [11,12]. By reducing the effects of these enzymes, curcumin has shown to prevent the inflammation symptoms of many diseases like arthritis and alzheimer's disease [13]. Furthermore, various studies using rat models showed the accelerated wound healing activity of curcumin owing to its powerful anti-oxidant property. Also the ability of curcumin to assist wound healing in diabetic mice has been well demonstrated by various groups. Where curcumin treatment in diabetic wound demonstrated an increased formation of granulation tissue, neovascularization and enhanced biosynthesis of extracellular matrix (ECM) proteins, such as collagen [14]. Similarly, Panchatcharam et al in rat model demonstrated on treatment of curcumin, lipid peroxides (LPs) was decreased, while the levels of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), activities were significantly increased exhibiting the antioxidant properties of curcumin in accelerating wound healing [4]. These observations demonstrated, curcumin has a property to scavenge free radicals, which is the major cause of inflammation during wound healing activity. Despite these unique biological activities, a major problem associated with curcumin delivery is its extreme low solubility in aqueous solubility in aqueous solutions, which limits its bioavailability and clinical efficacy [8,11,12]. One possible method to achieve this paradigm is encapsulating and delivering curcumin to inflammatory site with wound dressing sponge. This sponge are fabricated with various biocompatible and biodegradable materials, such as alginate, chitosan, gelatin and poly (ethylene glycol) and recently gained the attention in pharmaceutical and biomedical arena, as matrices for wound dressings [15,16]. Many types of polymers have been used for drug delivery system but the requirements of the biocompatibility and biodegradability have limited the choice of polymers used in clinical application. Some representatives of such materials are chitosan and alginate. Chitosan is a natural cationic mucoadhesive polymer, is biologically renewable, biodegradable, biocompatible, nonantigenic, nontoxic, and biofunctional. It can accelerate the wound healing process by enhancing the functions of inflammatory cells like macrophages and fibroblasts. It could inhibit nitric oxide production that has been shown to contribute to cytotoxicity in cell proliferation during inflammation of wound healing by the activated RAW 264.7 macrophages and allow the formation of granulation tissue with angiogenesis [17]. Furthermore, it is a penetration enhancer which can provide maximum bioavailability of delivered drug, at wound site [18]. Whereas, Alginate is an anionic polymer with additional characteristics like biocompatible, hydrophilic, and biodegradable under normal physiological conditions [18]. It is able to maintain a physiologically moist microenvironment that promotes healing and the formation of granulation tissue and achieves homeostasis [15,16]. In recent year the alginate-chitosan (AC) sponge with entrapped therapeutics are of special interest for wound healing purposes owing to their biocompatibility, biodegradaibility and ability to sustain therapeutic drug levels for prolonged periods of time. Moreover, its polymeric matrix can prevents the degradation of the drug, by protecting the encapsulated curcumin against hydrolysis and biotransformation for a longer time. Beside low aqueous solubility, the major concerned associated with curcumin delivery is its severe biodegradation and instability in biological pH. In this regard, coating the drug with large molecules, such as surfactants containing long-chain hydrocarbons, helps to provide more effective stabilization of entrapped drug in biological medium. Therefore research groups are using long chain surfactant such as oleic acid (OA) and its salt for the stabilization of various drug delivery systems.
In this scenario, the current approach was to prepare and characterize curcumin loaded sponge composed of oleic acid, chitosan and sodium alginate. We hypothesized that the hydrophobic drug curcumin would partition in to the coated oleic acid shell. Whereas, alginate and chitosan anchors at the interface of the OA shell and give the aqueous dispersibility and easy load of hydrophobic anticancer drug curcumin. Here the positively charged chitosan can be easily complexed with negatively charged polyanions sodium alginate to form porous AC sponge through the interionic interaction. The large surface area of the sponge facilitates the interaction with the healing tissue, thereby serving as a substrate for the sustained delivery of curcumin as well as improves wound healing by protecting tissues from oxidative damage. Thus, the aim of the present study is to evaluate the biological activity of the formulated curcumin-loaded AC sponge using in vitro and in vivo methods.